In C. H. George U.S. Pat. No. 3,856,654, herein incorporated by reference, there is disclosed one particular type of sputtering machine of background interest, having a cylindrical sputtering chamber within which a perforated cylindrical cathode ring is mounted so that a sputtering gas is ejected through apertures in the cathode ring into the sputtering chamber toward an array of substrates to be sputtered. In certain modified versions of the George machine described in some detail hereafter under the heading "PRIOR ART - (B)," the sputtering gas is advanced through a series of interconnecting ducts within the walls of a negatively charged cathode cell assembly, including a perforated cathode ring integrally connected thereto and forming the outer surface thereof.
In any such machine, where the sputtering gas is to be advanced from a grounded supply line to a cathode cell input line at high negative voltage and low absolute pressure, a problem arises with unwanted sputtering glow which is established in the gas supply line at the region of voltage drop that must necessarily occur in the region between the grounded supply line and the charged cathode input, as discussed in some detail hereafter under the heading "PRIOR ART - (B)."
Certain prior art solutions to this problem, using a capillary tube in the supply line, have not been entirely successful as described hereafter under the heading "PRIOR ART - (C)."
A specific object of the invention is to provide an improved glow suppression device and method for sputtering machines of the general class in which the sputtering gas must be transported from a grounded supply line to a charged cathode cell.
More general objects are to provide improved glow-suppression devices and methods for any system wherein an ionizable gas or mixture of gasses is to be transported across a potential voltage difference under circumstances where the gas would otherwise tend to support a sputtering glow.